TempData support for Enum types

[anfomin]

SessionStateTempDataProvider does not support Enum types but enums always can be converted to the underlying type and serialized to JSON. May be temp data provider should support enums?

[Eilon]

@pranavkm can you see if this is straightforward to add? If it's crazy complex or something then we should push out. Not sure how well enums will roundtrip in this scenario.

[Krusen]

I actually had a look at this a few weeks ago.

The only "issue" seems to be getting the value back. The BsonReader in Json.NET casts the value to long even though it knows it is an int. This means you can't do this:

MyEnum myEnum = (MyEnum) TempData["myEnum"];

Instead you will have to do either of these:

myEnum = (MyEnum)(long) TempData["myEnum"];
myEnum = Enum.Parse(typeof(MyEnum), TempData["myEnum"].ToString());

As far as I remember this is actually also currently the same when just storing and int in TempData because of boxing - (int)(object)1L doesn't compile.

I couldn't see any good reason why BsonReader does this and I was going to raise an issue about it but never got around to it.

[pranavkm]

@Krusen I filed a bug in Json.Net for the BsonReader behavior - JamesNK/Newtonsoft.Json#692. For now, I was hoping to fix it by attempting to cast short-longs to ints since it also affects round tripping for regular int values.